1 The Birth of Science - MSRI

1.4 Was There “Science” in Classical Greece? 17
from surviving fragments, no theorems of atomic theory were demonstrated
by the ancient atomists, nor any true experiments carried out.
However we stress the following points:
– The explanation of phenomena by means of theories that have as objects
non-observable entities, such as the atoms of Leucippus and Democritus,
is a step of enormous importance toward the construction of
scientific theories.
– Many of the ideas destined to become keystones in science, Hellenistic
and modern alike, were born from the Greek thought of the classical
period. This is the case with mechanistic determinism, which appears
to go back to Leucippus, 30 and the distinction between primary and
secondary qualities, which appears in Democritus 31 and became an essential
foundation for the formulation of quantitative theories of phenomena
such as sound, color and the chemical properties of substances.
– Even some more specific ideas that are often considered scientific already
appear in the thought of the so-called pre-Socratic thinkers. 32 For
instance, science is indebted to the ancient atomists not only for the general
notion and the word “atom”, but also for ideas such as the chaotic page 41
motion of atoms (which, developed in the Hellenistic period and revived
in modern times, was essential in the creation of the kinetic theory
of gases) 33 or the existence of atoms with “hooks” that can connect
with one another, 34 a didactic image still used sometimes in chemistry
textbooks.
For another example, consider the “bucket experiment”, one of whose
variants consists in the observation that if a bucket full of water is rotated
in a vertical plane the water does not fall out. If instead the bucket rotates
around a vertical axis coinciding with its axis of symmetry, the surface of
the water takes on a characteristic concave shape. Either way one observes
30 Leucippus, fr. 2 in [Diels: FV].
31 Democritus, fr. 125 in [Diels: FV].
32 Among the philosophers traditionally called pre-Socratic we will be particularly interested in
Democritus, who in fact survived Socrates by several years.
33 See, for example, Diogenes Laertius, Vitae philosophorum, IX, 31, where the idea is attributed
to Leucippus. It would be interesting to know the origin of the notion of chaotic motion of atoms.
A stupendous passage in Lucretius about disordered motion of dust lit by a sunbeam (De rerum
natura, II, 112–141) gives an indication of the type of phenomena that might have suggested the
idea. Lucretius mentions the disordered and extremely fast motion of atoms as the ultimate cause
of the progressively slower motion of larger particles. It is interesting to compare the lucid explanation
reported by Lucretius with the vitalist explanation given in 1828 for a similar phenomenon
by the famous discoverer of Brownian motion; see [Brown].
34 The existence of atoms with hooks was postulated by Democritus, as we know from Aristotle’s
(lost) book On Democritus, a passage of which is reported by Simplicius (In Aristotelis De Caelo
commentaria, [CAG], vol. VII, 294, 33 = text 37 in [Diels: FV]).
Revision: 1.15 Date: 2002/09/12 02:47:10